Large electrical generators are cooled by a gas stream that flows througout the generator. when a malfunction occurs the particular area involved will overheat. Organic materials in the overheated area are affected first and degrade, producing particulates (i.e., "thermoparticulate") which enter the gas stream. Special compounds can be placed throughout the generator which thermoparticulate at much lower temperatures than most organic materials used in the generator.
A portion of the gas stream is diverted to a monitor which detects the presence of particulates in the gas stream and sounds an alarm. It may also open a valve so that a portion of the gas stream passes through a filter which collects a sample of the particulates. The sample is analyzed to determine which of the thermoparticulating compounds placed throughout the generator has degraded, thus pinpointing the area of malfunction. A better decision can then be made as to whether to reduce the load on the generator or shut it down, and if the latter, repair time is greatly reduced since one knows where to look.
Collecting samples and analyzing them requires a certain amount of time, but when the alarm goes off a decision must be made immediately at least as to whether or not to reduce the load on the generator. Failure to reduce the load should a true emergency exist may mean extensive damage to the generator. On the other hand, any reduction in load constitutes an immediate loss of electricity generated. The operator may be reluctant to base such a weighty decision on an unconfirmed alarm from a single monitor.